The Substitution of Al and F in Titanite at High Pressure and Temperature: Experimental Constraints on Phase Relations and Solid Solution Properties |
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| Authors: | TROPPER PETER; MANNING CRAIG E; ESSENE ERIC J |
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| Institution: | 1DEPARTMENT OF GEOLOGICAL SCIENCES, UNIVERSITY OF MICHIGAN, 2534 C. C. LITTLE BUILDING, ANN ARBOR, MI 48109-1063, USA
2DEPARTMENT OF EARTH AND SPACE SCIENCES, GEOLOGY BUILDING, UNIVERSITY OF CALIFORNIA AT LOS ANGELES, LOS ANGELES, CA 90095-1567, USA |
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| Abstract: | Experimental studies were carried out to evaluate phase relationsinvolving titanite–F–Al-titanite solid solutionin the system CaSiO3–Al2SiO5–TiO2–CaF2. Theexperiments were conducted at 900–1000°C and 1·1–4·0GPa. The average F/Al ratio in titanite solid solution in theexperimental run products is 1·01 ± 0·06,and XAl ranges from 0·33 ± 0·02 to 0·91± 0·05, consistent with the substitution TiO2+]–1AlF2+]1.Analysis of the phase relations indicates that titanite solidsolutions coexisting with rutile are always low in XAl, whereasthe maximum XAl of titanite solid solution occurs with fluoriteand either anorthite or Al2SiO5. Reaction displacement experimentswere performed by adding fluorite to the assemblage anorthite+ rutile = titanite + kyanite. The reaction shifts from 1·60GPa to 1·15 ± 0·05 GPa at 900°C, from1·79 GPa to 1·375 ± 0·025 GPa at1000°C, and from 1·98 GPa to 1·575 ±0·025 GPa at 1100°C. The data show that the activityof CaTiSiO4O is very close to the ideal molecular activity model(XTi) at 1100°C, but shows a negative deviation at 1000°Cand 900°C. The results constrain |
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